1. Field of the Invention
Apparatuses and methods consistent with the present invention relate to a data storage device and a method of operating the data storage device, and more particularly, to a data storage device using magnetic domain wall movement of a magnetic material and a method of operating the data storage device.
2. Description of the Related Art
A magnetic minute area included in a ferromagnetic body is referred to as a magnetic domain. The direction of a magnetic moment is identical in the magnetic domain. The size and magnetization direction of the magnetic domain can be appropriately controlled by the properties, shape and size of the magnetic material and an external energy applied to the magnetic material.
A magnetic domain wall is a boundary area between magnetic domains having different magnetization directions and has a predetermined volume. The magnetic domain wall can be moved by a magnetic field or current applied to the magnetic material. That is, a plurality of magnetic domains having particular magnetization directions can be formed in a magnetic layer having predetermined width and thickness and the magnetic domains can be moved using a magnetic field or current having an appropriate strength.
A magnetic domain wall movement principle can be applied to a data storage device. When the magnetic domain wall movement principle is applied to a data storage device, since the magnetic domain wall movement allows the magnetic domains to pass by a read/write head, read/write operations are possible without rotation or any physical movement of a recording medium. An example of the data storage device in which the magnetic domain wall movement principle is applied has been introduced by U.S. Pat. No. 6,834,005 B1.
FIG. 1 is a perspective view of a conventional data storage device using the magnetic domain wall movement principle which was introduced in U.S. Pat. No. 6,834,005 B1. Referring to FIG. 1, the conventional data storage device using the magnetic domain wall movement principle (hereinafter, referred to as “conventional storage device”) includes a U-shaped magnetic layer 100. The magnetic layer 100 includes a storage area S formed of a plurality of magnetic domains that are arranged one after the other and a buffer area B having a length similar to that of the storage area S. In FIG. 1, the buffer area B is the right column part of the magnetic layer 100, but the position thereof may vary. A read head RH and a write head WH are provided under the middle portion of the magnetic layer 100.
Although it is not illustrated, the magnetic layer 100 is connected to a transistor used as a driving device. The direction of current applied to the magnetic layer 100 is controlled by the transistor. The direction of the magnetic domain wall movement is determined according to the direction of the current. The read/write operation is performed by pushing and pulling the magnetic domain walls by controlling the direction of the current.
However, the above-described conventional storage device has the following disadvantages.
First, since the conventional storage device, which performs the read/write operation by pushing and pulling the magnetic domain walls, requires the buffer area B to be as large as the storage area S, an effective storage capacity is only ½ of a physical storage capacity.
Second, when a read operation is performed by pushing the magnetic domain walls toward the buffer area B, for a next read operation, the magnetic domains of the buffer area B are pulled back toward the storage area S to return the position of the magnetic domains to their original state. Accordingly, power consumption increases and the read and write speed of data decreases.
Third, since the operation of pushing and pulling the magnetic domain walls is repeated, the characteristic of the magnetic domain wall is deteriorated and the life span of the storage device is shortened.
Fourth, since the U-shaped magnetic layer 100 is difficult to manufacture using present etching techniques, it is difficult to produce the conventional storage device. Furthermore, a plurality of notches need to be formed at regular intervals on the surface of the magnetic layer 100 to secure the stability of the magnetic domain wall movement. However, it is very difficult to uniformly form the fine notches on the U-shaped magnetic layer 100.
Therefore, the problems of the conventional storage device stem from the pushing and pulling of the magnetic domain walls and the U shape of the magnetic layer 100.